Patent Application
20220056061
The invention relates to a method for the production of compounds according to the general formula [W(NtBu)2(NRARB)2] which hereinafter are also referred to as bis(tertbutylimido)bis(dialkylamido)tungsten compounds or bis(tertbutylimido)bis(dialkylamido)tungsten complex. RA and RB are independently selected from the group consisting of linear and branched alkyl radicals having 1 to 20 carbon atoms. The subject matter of the invention are also compounds according to the general formula [W(NtBu)2(NRARB)2], obtainable according to the claimed method, compounds according to the general formula [W(NtBu)2(NRARB)2], with the exception of [W(NtBu)2(NMe2)2] and [W(NtBu)2(NEtMe)2], the use of a compound [W(NtBu)2(NRARB)2] and a substrate which, on a surface, has a tungsten layer or a tungsten-containing layer.
Tungsten layers and tungsten-containing layers are important inter alia in semiconductor, solar, TFT LCD and flat screen technology. Tungsten nitride layers, for example, constitute good copper diffusion barriers for microelectronic components. Due to its low electrical resistance and its resistance to copper, tungsten nitride constitutes a comparatively promising barrier material. Thin tungsten nitride films can also be used as electrodes for thin-film capacitors and field-effect transistors.
In the semiconductor industry, in particular, the growth of tungsten nitride layers with a low specific resistance and an excellent step coverage is pursued. Vapor deposition methods are typically used to produce such tungsten nitride layers, other tungsten-containing layers, such as, for example, layers or films of WON, WSi, WSiN and WO as well as pure tungsten layers. Most commonly, different ALD methods (atomic layer deposition) and CVD methods (chemical vapor deposition) are used.
Here and hereinafter, the specification of an exact stoichiometry of the depositable tungsten-containing layers or films has been dispensed with. Moreover, the term “layer” is used synonymously with the expression “film” and does not make any statement about the layer thickness or the film thickness.
The deposition of tungsten nitride layers by means of an ALD method was described, for example, in year by 2000 Klaus et al. (J. W. Klaus, S. J. Ferro, S. M. George, J. Electrochem. Soc. 2000, 147, 1175-1181). Based on WF6 and NH3, tungsten nitride layers having a good step coverage were obtained. However, the disadvantage of this method is that WF6 and/or the by-product hydrogen fluoride produced during the process particularly attacks substrates which consist of silicon or contain silicon. In addition, fluorine impurities on the surface of the tungsten nitride layer can negatively influence the adhesion of copper that is desired later.
The bis(alkylimido)bis(dialkylamido)tungsten compound [W(NtBu)2(NMe2)2], for example, is known in the prior art as a halogen-free precursor for the deposition of tungsten nitride layers. In 2003, Becker et al, reported on its synthesis and application as a precursor in an ALD process. (J. S. Becker, S. Suh, S. Wang, R. G. Gordon, Chem. Mater. 2003, 15, 2969-2976)
The synthesis route for preparing [W(NtBu)2(NMe2)2] published by Becker et al. comprises three stages and is used by the authors analogously for the production of [W(NtBu)2(NMeEt)2]. In the first step for the production of [W(NtBu)2(NMeEt2)2], commercially available WCl6 with four equivalents of HN(tBu)(SiMe3) is reacted in toluene to half an equivalent of mixed-substituted tert-butylamine adduct [W(NtBu)2Cl2(NH2tBu)]2. To isolate and purify this first intermediate, a filtration step for separating (tBu)(Me3Si)NH2Cl and unreacted WCl6 as well as a crystallization step are provided inter alia. The second stage involves the reaction of half an equivalent of [W(NtBu)2Cl2(NH2tBu)]2 with two equivalents of pyridine in diethyl ether In this case the pyridine adduct [W(NtBu)2Cl2(py)2] is obtained with the release of tert-butylamine (tBuNH2). To isolate this second intermediate, the solvent diethyl ether, tBuNH2 and excess pyridine must be removed in a vacuum, which is problematic because of the high boiling temperature of pyridine. For the third and last reaction step, the educt lithium dimethylamide (LiNMe2) must first be prepared in a separate synthesis. This is because the target compound [W(NtBu)2(NMe2)2] is produced by reacting an equivalent of [W(NtBu)2Cl2(py)2] with two equivalents of LiNMe2 in diethyl ether. This third step is described as very violent and exothermic. Purification of the product [W(NtBu)2(NMe2)2] includes a filtration step for separating the LiCl load produced during the reaction and excess LiNMe2. Furthermore, two distillations under reduced pressure are provided. The compounds [W(NtBu)2(NMe2)2] and [W(NtBu)2(NEtMe)2] are each described as a pale yellow liquid. No indication of the respective overall yield is given in the literature.
A significant disadvantage of the known method for preparing the bis(alkylimido)bis(dialkylamido)tungsten compound [W(NtBu)2(NMe2)2] is the plurality of reaction steps and the effort and time associated with each of the three synthesis steps. Two intermediates are produced and isolated, namely [W(NtBu)2Cl2(NH2tBu)]2 and [W(NtBu)2Cl2(py)2]. Their isolation and/or purification in each case comprises at least one time and/or labor-intensive step. In addition, the educt LiNMe2 is to be produced in a separate reaction for the third synthesis stage. A further disadvantage is that, inter alia, the solvents diethyl ether and pyridine, which are in principle capable of coordination, are used. In the third step in particular, the use of diethyl ether as solvent is disadvantageous because the removal of the LiCl load produced as by-product and of the excess LiNMe2 can consequently be difficult, or at least harder. If lithium ions are present in the reaction mixture, lithium tungstate complex salts can also be formed, which are likewise difficult to separate or cannot be separated at all. With a view to an industrial application of bis(alkylimido)bis(dialkylamido)tungsten compounds and a synthesis thus required on an industrial scale, the third synthesis step in particular is disadvantageous, especially since it is described as very violent and exothermic and is, therefore, at least to be classified as critical for safety reasons.
Moreover, the procedure known in the literature provides a complex purification of the end product [W(NtBu)2(NMe2)2] or [W(NtBu)2(NMe2)2] by means of a filtration step and two distillations. Nevertheless, the products obtained in this way can have not precisely quantifiable salt impurities, in particular lithium impurities. Unlike the product in pure form, its properties can therefore be altered or impaired in an uncontrollable and in some cases irreversible manner. It is unknown whether, with the reaction control described above, yields are obtained which are satisfactory with a view to industrial use of said compound.
On the whole, the synthesis route documented in the literature can be classified as unsatisfactory from ecological and economic perspectives.
The object of the invention is therefore to overcome these and further disadvantages of the prior art and to provide a method by means of which defined bis(alkylimido)bis(dialkylamido)tungsten compounds can be produced easily, efficiently, economically and reproducibly in high purity and good yields. In particular, the purity of the bis(alkylimido)bis(dialkylamido)tungsten compounds, which can be produced by the method, should satisfy the requirements for precursors for the production of high-quality substrates which have tungsten layers or tungsten-containing layers. The method is to be characterized by the fact that it can also be carried out on an industrial scale with a comparable yield and purity of the target compounds. In addition, novel bis(alkylimido)bis(dialkylamido)tungsten compounds are to be provided. Furthermore, a substrate is to be provided which, on a surface, has a tungsten layer or a tungsten-containing layer, which can be produced using a bis(alkylimido)bis(dialkylamido)tungsten compound obtainable or obtained by the claimed method or using one of the novel bis(alkylimido)bis(dialkylamido)tungsten compounds.
The main features of the invention are set forth in claim 1 or any one of claims 22 through 33. The embodiments are the subject of claims 2 through 21.
The object is achieved by
a method for the production of bis(alkylimido)bis(dialkylamido)tungsten compounds
according to the general formula
[W(NtBu)2(NRARB)2] (I),
wherein
RA and RB are independently selected from the group consisting of linear and branched alkyl radicals having 1 to 20 carbon atoms,
comprising the following steps:
a) provision of [W(NtBu)2(NHtBu)2]
and
b) reaction of [W(NtBu)2(NHtBu)2] from step a) with an amine according to the general formula HNRARB in a solvent MU,
wherein
In this case, the general formula I includes both the monomers and any oligomers.
The alkyl radicals RA and RB may also be substituted, for example be partially or fully halogenated.
The solvent MU may also be a solvent mixture comprising two or more solvents.
The claimed method advantageously allows the production of the target compounds [W(NtBu)2(NRARB)2] (I) in a simple two-stage synthesis.
By reacting one molar equivalent of the compound [W(NtBu)2(NHtBu)2] provided in step a) with an excess of the amine HNRARB in the solvent MU, the respective bis(tertbutylimido)bis(dialkylamido)tungsten complex is obtained in step b). Here, excess means that more than two molar equivalents HNRARB, which are technically required for the production of [W(NtBu)2(NRARB)2] (I), are provided. The molar ratio [W(NtBu)2(NHtBu)2]:HNRARB is thus less than 1:2, i.e. less than 0.5. The level of the excess of HNRA RB to be selected depends, in particular, on the reactivity of the secondary amine used respectively in step b) as educt, in particular taking into account the reaction parameters otherwise selected, such as for example the solvent or solvent mixture.
In the claimed two-stage synthesis, after step b) has been carried out only the desired bis(tertbutylimido)bis(dialkylamido)tungsten compound of the type [W(NtBu)2(NRARB)2] (I) and the defined, comparatively easily separable by-product tBuNH2 and amine HNRARB that is unreacted, i.e. used in excess, are present. The tBuNH2 obtained in step b) is comparatively highly volatile and can thus be quantitatively removed in a simple manner, namely by applying a slight negative pressure to an interior of the respective reaction vessel. The same generally applies to the HNRARB used in excess in step b), in particular to very highly volatile amines, such as, for example, HNMe2.
Furthermore, it is advantageous that—due to the absence of lithium compounds, particularly LiCl—no undefinable by-products are formed, for example lithium tungstate complex salts, which can only be separated with difficulty or not at all. The respective target compound of the type [W(NtBu)2(NRARB)2] (I) in solution can be reacted directly with one or more reactants. Alternatively, the compound of the type [W(NtBu)2(NRARB)2] (I) can be isolated easily, for example, by removing all volatile constituents. Furthermore, the isolated compound—as per an NMR spectroscopic examination—has neither amine impurities nor residues of the solvent or solvent mixture used. The respective target compound can thus be used and/or stored after isolation without further purification. The reproducible yield is satisfactory for [W(NtBu)2(NMe2)2], for example—even when upscaling to an industrial scale.
As a whole, the method claimed overcomes the disadvantages of the prior art. In particular, no difficult-to-separate salt loads are obtained, such as, for example, LiCl in diethyl ether. Potentially coordinating solvents, such as pyridine and diethyl ether, are dispensed with completely. The method is characterized by a particularly simple and economical method because it is a simple two-stage synthesis. In addition, few process steps that are easily accomplished in terms of preparation are necessary. Only educts that are commercially easily available, synthetically relatively easily accessible and relatively economical are used, Only by-products that are definable and separable easily and quantitatively are formed. In particular, non-separable lithium tungstate complex salts are not formed. Therefore, compounds of the type [W(NtBu)2(NRARB)2] (I), such as, for example, bis(tertbutylimido)bis(dimethylamido)tungsten, are obtained reproducibly in high purity, even without any further distillative and/or sublimative purification. However, transcondensation and/or distillation and/or sublimative purification may be provided, for example. The bis(tertbutylimido)bis(dialkylamido)tungsten compounds obtainable by the claimed method meet the purity requirements for precursors for the production of high-quality substrates which have tungsten layers or tungsten-containing layers. In particular, the compounds of the type [W(NtBu)2(NRARB)2] (I), which can be produced by the claimed method, do not inherently have lithium impurities, namely due to the omission of educts, such as, for example, lithium dimethylamide. In addition, the method can also be carried out on an industrial scale, wherein comparable yields and purities of the target compounds are achieved. The method claimed saves time, energy and costs in comparison. On the whole, it can be classed as comparatively more (atom-)economical and more ecological.
In one embodiment of the claimed method for the production of bis(tertbutylimido)bis(dialkylamido)tungsten compounds according to the general formula [W(NtBu)2(NRARB)2] (I), RA and RB are independently selected from the group consisting of Me, Et, nPr, Pr, nBu, tBu, sBu, iBu, CH2sBu, CH2iBu, CH(Me)(iPr), CH(Me)(nPr), CH(Et)2, C(Me)2(Et), C6H11, CH2C6H5 and C6H5.
In a further embodiment of the claimed method, the provision of [W(NtBu)2(NHtBu)2] in step a) a reaction of WCl6 with tBuNH2 in the presence of an auxiliary base in an aprotic solvent MA. Here, a molar ratio WCl6:tBuNH2 is ≤1:4.
The inexpensive, commercially available WCl6 is used as educt. On this basis, a production of the intermediate [W(NtBu)2(NHtBu)2] is accomplished by reaction with at least four molar equivalents of tBuNH2 in the aprotic solvent MA. The hydrogen chloride obtained thereby as a single by-product is absorbed by means of an auxiliary base contained in the reaction mixture.
In principle, any compound which, under the reaction conditions selected in each case, is capable of quantitatively absorbing the hydrogen chloride produced during the respective reaction, can be used as an auxiliary base. The auxiliary base must be characterized, in particular, by the fact that it does not affect the pH of the reaction mixture and the water content of the reaction medium and, with respect to the educts WCl6 and tBuNH2 as well as to the desired intermediate [W(NtBu)2(NHtBu)2], does not act as a reactant. In addition, any excess of the auxiliary base used must be easily quantitatively removable from the reaction mixture and the product obtained by the reaction of the auxiliary base with the hydrogen chloride must likewise be easily quantitatively separable. A molar ratio WCl6:auxiliary base is selected such that at least six molar equivalents of hydrogen chloride can be absorbed.
In the simplest case, tBuNH2 is both reactant or educt and auxiliary base. Then, the hydrogen chloride formed during the reaction reacts with the amine tBuNH2 used in excess to form tBuNH3Cl. Excess in this context means that per molar equivalent of WCl6 at least ten—instead of the four that are technically required for obtaining [W(NtBu)2(NHtBu)2]—equivalents of tBuNH2 can be used. The molar ratio WCl6:tBuNH2 is in this simplest case therefore ≤1:10. Any possibly unreacted tBuNH2 can be removed simply by applying a negative pressure to an interior of the respective reaction vessel. Alternatively, it can be provided for the auxiliary base to only comprise the amine tBuNH2, i.e. part of the auxiliary base tBuNH2 is replaced by another auxiliary base. The overall molar ratio of Was tBuNH2 provided in the reaction mixture is then <1:4 and >1:10, i.e. <0.25 and >0.10.
The term reaction vessel in the context of the present invention is not limited to a volume, a material composition, equipment or a form.
After carrying out the reaction of WCl6 with tBuNH2 in the presence of an auxiliary base, only the desired intermediate [W(NtBu)2(NHtBu)2] and defined, comparatively easily separable by-products, typically an ammonium salt, for example tBuNH3Cl, and potentially tBuNH2 that is unreacted, i.e. used in excess, are present. Any tBuNH2 still present in the reaction mixture can be removed easily by applying a negative pressure to an interior of the respective reaction vessel. The relatively easy separability of the precipitated ammonium salt, for example tBuNH3Cl, can also be explained by the advantageous selection of the aprotic solvent MA.
One embodiment of the method provides that the aprotic solvent MA is selected from the group consisting of hydrocarbons, benzene and benzene derivatives. The first solvent is for example selected from the group consisting of n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, cyclopentane, cyclohexane, cycloheptane, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, cyclohexene, benzene, toluene, xylene and isomers thereof. The aprotic solvent MA is preferably n-hexane, i-hexane or n-heptane or a mixture comprising at least one of said solvents. Advantageously, the aforementioned solvents, in particular benzene and toluene, can be completely recycled without losses. This has a positive effect on the environmental balance of the method.
In a further variant of the claimed method, in step a) the reaction of WCl6 with tBuNH2 in the presence of the auxiliary base, in the aprotic solvent MA comprises the following steps of:
i) providing a solution of tBuNH2 in the aprotic solvent MA,
ii) adding the auxiliary base,
iii) adding WCl6,
wherein during the addition and/or after the addition of WCl6, a reaction of WCl6 with tBuNH2 takes place.
The aprotic solvent MA may also be a mixture of solvents.
Preference is given to the auxiliary base tBuNH2, wherein a molar ratio WCl6:auxiliary base tBuNH2 is ≤1:6. Therefore, together with the tertbutylamine required as reactant for the production of [W(NtBu)2(NRARB)2] (I), a molar ratio WCl6:tBuNH2 is ≤1:10. If tBuNH2 functions both as educt and as auxiliary base, the process is particularly simple. On the one hand, the number of chemicals required is reduced. On the other hand, step i), namely the provision of a solution of tBuNH2 in the aprotic solvent MA, and step ii), namely the addition of the auxiliary base, take place in a single step.
If, in another embodiment of the claimed method, an auxiliary base other than the amine tBuNH2 is used, it can be provided that this auxiliary base is added in the separate step ii). The auxiliary base is added in bulk, i.e, generally as a solid or liquid, or as a suspension or solution in a solvent SR. The solvent SH is identical or miscible with the aprotic solvent MA.
In the context of the present invention, two solvents are referred to as miscible if they are miscible at least during the respective reaction, that is, are not present as two phases.
In one embodiment of the claimed method, it is provided that in step iii) Was is suspended in a solvent SW or added as a solid. The solvent SW is identical to or miscible with the aprotic solvent MA. The addition of WCl6 as a suspension in the solvent SW can, as a function of the other reaction parameters, be advantageous for better control of the course of the reaction or of the exothermic reaction. The addition is then effected, for example, using a dosing device, in particular by adding a drop at a time or injecting. If WCl6 is added as a solid, a funnel or a funnel-like device, for example, is provided for the addition. In the alternative or in addition, a shut-off valve and/or a stop valve can be provided in a supply line of the respective reaction vessel, irrespective of the form in which WCl6 is added.
In yet another embodiment of the claimed method, in step i) WCl6 is provided or added as a suspension in the aprotic solvent MA. If tBuNH2 is provided as auxiliary base, step ii) and step iii) take place in a single step. In this case, tBuNH2 is added as a solution in a solvent SR or as a liquid, that is, without addition of a solvent, in each case, for example, by adding a drop at a time or injecting. The solvent SR is identical or miscible with the aprotic solvent MA. If an auxiliary base other than tBuNH2 is provided, this auxiliary base is added in the separate step ii). The auxiliary base is added in substance, i.e. generally as a solid or liquid, or as a suspension or solution in a solvent SB. The educt tBuNH2 is then added in step iii) as a solvent SP or as a liquid, that is, without addition of a solvent, in each case, for example, by adding a drop at a time or injecting. In this case, the solvents SB and SP are each identical to or miscible with the aprotic solvent MA.
Depending on the choice of aprotic solvent or solvent mixture MA and the other reaction conditions, such as, for example, addition form of WCl6, that is, as a substance or as a suspension, rate of addition of WCl6, stirring speed, internal temperature of the respective reaction vessel, the WCl6 reacts with tBuNH2 in the presence of the auxiliary base already during the addition and/or after the addition of WCl6.
In another variant of the claimed method, the reaction of WCl6 with tBuNH2 in the presence of the auxiliary base, in particular tBuNH2, in the aprotic solvent MA is carried out at a temperature TU, wherein the temperature TU is between −30° C. and 100° C.
Temperature TU means the internal temperature TU of the respective reaction vessel.
Owing to the exothermicity of the reaction, it may be advantageous to select comparatively low rates for the addition of WCl6 and/or the temperature TU. In the alternative or in addition, it may be provided that a suspension of
WCl6 is added in an aprotic solvent or solvent mixture. The respective procedure is to be selected taking into account the other reaction parameters, such as, for example, the tBuNH2 concentration (educt) and the solvent or solvent mixture.
In a further embodiment of the method, the temperature To of the during the reaction of WCl6 with tBuNH2 in the presence of the auxiliary base, especially tBuNH2, is between −20° C. and 80° C. In yet another embodiment of the method, the temperature TU during the reaction of WCl6 with tBuNH2 in the presence of the auxiliary base, especially tBuNH2, is between −10° C. and 50° C.
An internal temperature of the respective reaction vessel can be determined by means of a temperature sensor or a plurality of temperature sensors for one or more regions of the reaction vessel. At least one temperature sensor is provided for determining the temperature TU, which generally corresponds to an average temperature To of the reaction mixture.
In a further variant of the method, the temperature TU is regulated and/or controlled using a heat transfer medium WU. For this purpose, a cryostat can be used, for example, which contains a heat transfer medium, which ideally can function both as a coolant and as a heating medium. Through the use of the heat transfer medium WU, deviations of the temperature TU from a set value TS1 defined for the reaction of WCl6 with tBuNH2 in the presence of the auxiliary base, in particular tBuNH2, can be absorbed or compensated for as much as possible. Typical device deviations render it hardly possible to realize a constant temperature TU. Through the use of the heat transfer medium WU, however, the reaction of WCl6 with tBuNH2 in the presence of the auxiliary base, especially tBuNH2, can take place at least within a preselected temperature range or within a plurality of preselected temperature ranges. For example, depending on the remaining reaction parameters, it may be advantageous to provide a temperature program for even better control of the course of the reaction or the exothermic reaction. In this case, for example, a lower temperature or a lower temperature range can be selected during a first phase of the addition of WCl6 than in a second phase of the addition of WCl6. It is also possible to provide more than two phases of the addition and thus more than two preselected temperatures or temperature ranges. Depending on the choice of other reaction conditions, such as, for example, the tBuNH2 concentration (educt) and the solvent or solvent mixture, it may be favorable during the addition and/or after the addition of WCl6 to increase the temperature TU using the heat transfer medium WU. This may make it possible to ensure that the reaction of WCl6 with tBuNH2 in the presence of the auxiliary base, especially tBuNH2, is carried out quantitatively.
If the provision of [W(NtBu)2(NHtBu)2] in step a) comprises a reaction of WCl6 with tBuNH2 in the presence of an auxiliary base in an aprotic solvent MA, a further variant of the claimed method provides for a filtration step to be performed prior to the reaction of [W(NtBu)2(NHtBu)2] in step b). The filtration step or decanting takes place, in particular, to separate the ammonium salt, especially tBuNH3Cl, produced during the reaction of WCl6 with tBuNH2 in the presence of an auxiliary base, especially tBuNH2. If, for example n-hexane, i-hexane and/or n-heptane are used as solvent, the ammonium salt, for example tBuNH3Cl, is precipitated quantitatively, while the intermediate [W(NtBu)2(NHtBu)2] remains in solution. Within the context of isolating the intermediate [W(NtBu)2(NHtBu)2], several filtration steps can also be provided, optionally also one or more filtrations over a cleaning medium, e.g. activated carbon or silica, e.g. Celite®. The filter cake comprising the ammonium salt load may be washed with a small amount of a volatile solvent to extract any product possibly contained in the ammonium salt load. Contamination of the bis(tertbutylimido)bis(dialkylamido)tungsten complex to be produced in step b) by the resulting ammonium salt load, for example tBuNH3Cl, is thus advantageously avoided.
Another variant of the method provides for [W(NtBu)2(NHtBu)2] to be isolated prior to the reaction of [W(NtBu)2(NHtBu)2] in step b). Isolating may comprise removing all volatile constituents, that is, the solvent or solvent mixture MA and any tBuNH2 that is unreacted i.e. used in excess. In a further embodiment of the claimed method, isolating [W(NtBu)2(NHtBu)2] comprises applying a negative pressure pw to an interior of the reaction vessel. The negative pressure pW, as a function of the other reaction conditions, in particular as a function of the solvent, is, for example, 10−3 to 101 mbar. This makes it possible, for example, to completely or almost completely separate and recycle the solvent or solvent mixture from step a). This is particularly advantageous from an economical and ecological point of view.
Isolating may comprise further method steps, such as, for example, the reduction of the mother liquor volume, i.e. concentration, for example by means of “bulb-to-bulb”, the addition of a solvent and/or a solvent exchange to precipitate the product from the mother liquor and/or to remove impurities and/or educts, washing and drying of the product. Furthermore, it may be provided that isolation comprises distillation and/or sublimation and/or crystallization and/or recrystallization.
In principle, no purification is required for a later reaction of [W(NtBu)2(NHtBu)2], in particular according to step b) of the method claimed here. If purification is still desired and/or necessary, the isolation may comprise distillation and/or sublimation and/or crystallization and/or recrystallization. The sublimation of [W(NtBu)2(NHtBu)2] can be carried out comparatively easily and quickly. In addition, as a result of the sublimation of [W(NtBu)2(NHtBu)2], a significant increase in the yield can advantageously be achieved, unlike in the recrystallization from toluene described in the literature (see embodiment 1).
This isolated and optionally purified compound [W(NtBu)2(NHtBu)2] can also be stored for later use.
In a further embodiment of the claimed method, in step b) the molar ratio [W(NtBu)2(NHtBu)2] HNRARB is ≤1:4. Even with a molar ratio of precisely 1:4, i.e. 0.25, a comparatively great excess of the amine is used HNRARB, namely twice as many molar equivalents of this educt than are technically required. The level of the excess of HNRA RB to be selected in individual cases depends, in particular, on the reactivity of the secondary amine used respectively in step b) as educt, in particular taking into account the otherwise selected reaction parameters, such as, for example, the solvent or solvent mixture.
In another embodiment, the solvent MU comprises an aprotic solvent. Another embodiment of the claimed method provides for the solvent MU to be miscible with or identical to the aprotic solvent MA. In this context, the term “identical” has two different meanings, as can be inferred from the explanations in the following paragraph.
After completion of step a), the present reaction mixture can, for example, be subjected to a filtration step in order to separate off the ammonium salt, for example tBuNH3Cl, which is produced as a by-product. For this purpose, the filtrate containing the raw product [W(NtBu)2(NHtBu)2] from step a), can, for example, be collected in another vessel and, after separation of the ammonium salt, e.g. tBuNH3Cl, be transferred into the respective reaction vessel again. This can take place, for example, by means of a pumping operation. In this case, the solvent MU comprises the aprotic solvent MA or, if no further solvent is added, is identical thereto. It can, furthermore, be provided for the aprotic solvent or solvent mixture MA to be removed by applying a negative pressure to an interior of the respective reaction vessel, and to not be returned. This is necessary, for example, if, for the reaction according to step b), a solvent MU is preferred, which is different from the aprotic solvent MA. In the event that the raw product [W(NtBu)2(NHtBu)2], after removal of the aprotic solvent MA, potentially still has residues of said solvent, it is advantageous for the further reaction according to step b) if the solvent MU is miscible with the solvent MA. The term “miscible” has already been defined above. If the raw product from step a) was isolated intermediately, optionally purified and stored, it can, for the reaction according to step b), depending on the selection of the other reaction conditions, also be dissolved in a solvent MU which is identical to the aprotic solvent MA. If, for example, n-hexane was used as aprotic solvent MA, n-hexane can, in turn, be used as solvent MU, wherein the latter may optionally, but does not have to, be recycled from the process.
In a variant of the claimed method, the aprotic solvent comprising the solvent MU, is selected from the group consisting of hydrocarbons, benzene and benzene derivatives. For example, the aprotic solvent comprising the solvent MU is selected from the group consisting of n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, cyclopentane, cyclohexane, cycloheptane, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, cyclohexene, benzene, toluene, xylene and isomers thereof. Preference is given to n-hexane, i-hexane and n-heptane and also to solvent mixtures comprising at least one of these solvents.
Yet another embodiment of the claimed method provides for the solvent MU to comprise a reactive solvent. In the context of the present invention, the term “reactive solvent” means a solvent which is not chemically inert. Under the respective reaction conditions, the reactive solvent can react with a potential reactant, for example with an educt and/or a product. The type and extent of the reactivity of the reactive solvent are dependent on the concentration of the reactive solvent present in the respective reaction mixture, the potential reactants, the concentration and reactivity of the potential reactants present in the respective reaction mixture and the other reaction conditions selected in each case.
In a further variant of the claimed method, the reactive solvent comprises the amine HNRARB. In another embodiment of the claimed method, it is provided for the solvent MU to constitute a solvent mixture comprising the amine HNRARB as the reactive solvent and at least one aprotic solvent. Here, the at least one aprotic solvent is selected from the group consisting of n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, cyclopentane, cyclohexane, cycloheptane, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, cyclohexene, benzene, toluene, xylene and isomers thereof. Decisive for the selection of the aprotic solvent is that the amine HNRARB and the aprotic solvent or solvent mixture are miscible, that is, are miscible at least during the reaction according to step b), that is to say, are not present as two phases.
A further embodiment of the claimed method provides that the molar ratio [W(NtBu)2(NHtBu)2] HNRA RB is between 1:200 and 1:10,000.
In yet another embodiment, the amine HNRARB itself is the reactive solvent. Then, the reaction of [W(NtBu)2(NHtBu)2] is carried out with HNRARB for example, in the amine HNRARB as educt or reactant, and the only solvent. At the same time, it is provided that the portion of the amine HNRARB used as solvent is recycled.
In another variant of the claimed method, step b) is carried out at a temperature TR and/or a pressure pR of the respective reaction vessel.
Temperature TR means the internal temperature TR of the respective reaction vessel and pressure pR means the internal pressure pR of the respective reaction vessel.
At the temperature TR and/or the pressure pR, at least a portion of a molar fraction of the amine NHRARB is present in liquid or dissolved form. In particular, it is provided that the at least one portion of the total molar fraction of the amine NHRARB used corresponds to the molar fraction of the amine NHRARB provided as educt, so that the reaction in step b) can proceed to completion. The temperature TR and the pressure pR are to be selected as a function of the amine NHRARB selected and of the other reaction conditions, e.g. selection of the solvent. The embodiment described here of the claimed method is provided, for example, when the amine NHRARB used has a comparatively low boiling point, such as, for example, dimethylamine. It is then advantageous for the implementation of step b), by adjusting the temperature TR and the pressure pR, in particular lowering the temperature TR or increasing the pressure pR, to transfer the respective amine into the liquid state and/or to hold it in this state for a certain time. Furthermore, the variant of the claimed method described here is advantageously provided when the amine NHRARB used both as educt and as reactive solvent is a solid or is present as a solid under the otherwise selected reaction conditions. In addition, this variant of the claimed method is advantageous if the amine NHRARB used exclusively as reactant is not miscible with, or soluble in, the in particular aprotic solvent MU under the otherwise selected reaction conditions.
In a further embodiment of the claimed method, in step b) the reaction of [W(NtBu)2(NHtBu)2] from step a) with the amine HNRARB in the solvent MU comprises the following steps of:
i) providing [W(NtBu)2(NHtBu)2]
The solvent MU can also be a solvent mixture, i.e. comprise two or more solvents.
In one embodiment of the method, in step b) ii) the amine HNRARB is added to the compound [W(NtBu)2(NHtBu)2] provided in step b) i)
A variant of the method provides that in step b) ii) the amine HNRARB is added using a dosing device. The addition can be effected, for example, by adding a drop at a time or injecting. In the alternative or in addition, a shut-off valve and/or a stop valve can be provided in a supply line of the respective reaction vessel. The addition of the amine HNRARB as solution in the, especially aprotic, solvent MU can, as a function of the other reaction parameters, be advantageous for better control of the course of the reaction or of the exothermic reaction.
Another variant of the method provides that a temperature TC is between −60° C. and 50° C. during the addition and/or after the addition of the amine HNRARB.
Temperature TC means the internal temperature TC of the respective reaction vessel.
In a further variant of the method, the temperature TC is between −40° C. and 30° C. during the addition and/or after the addition of the amine HNRARB. In yet another embodiment of the method, the temperature TC during the addition and/or after the addition of the amine HNRARB is between −30° C. and 20° C. At least one temperature sensor is provided for determining the temperature TC, which generally corresponds to an average temperature TD2 of the reaction mixture. The temperature sensor may be identical to the one for determining the temperature TU.
In a further embodiment of the method, the temperature TC is regulated and/or controlled using a heat transfer medium WC. For this purpose, a cryostat can be used, for example, which contains a heat transfer medium, which ideally can function both as a coolant and as a heating medium. Through the use of the heat transfer medium WC, deviations of the temperature TU from a set value TS2 defined for the period during the addition and/or after the addition of the amine HNRARB can be absorbed or compensated for as much as possible. Typical device deviations render it hardly possible to realize a constant temperature TC. Through the use of the heat transfer medium WU, however, the reaction of the [W(NtBu)2(NHtBu)2] provided in step a) with the amine HNRARB can at least be carried out within a preselected temperature range or within a plurality of preselected temperature ranges. For example, depending on the remaining reaction parameters, it may be advantageous to provide a temperature program or a temperature profile for even better control of the course of the reaction or the exothermic reaction. In this case, for example, a lower temperature or a lower temperature range can be selected during a first phase of the addition of the amine HNRARB than in a second phase of the addition of the amine HNRARB. It is also possible to provide more than two phases of the addition and thus more than two preselected temperatures or temperature ranges. After the addition, one or more phases can likewise be provided for incrementally increasing the temperature TC. Overall, a better control of the exothermic reaction or the course of the reaction is achieved by such a temperature program or temperature profile. In this way, the non-specific side reactions and/or degradation of the respective product [W(NtBu)2(NRARB)2] (I) can be prevented or at least reduced.
In yet another variant of the claimed method, [W(NtBu)2(NRARB)2] (I) is isolated after step b).
If the bis(tertbutylimido)bis(dialkylamido)tungsten compound according to the general formula [W(NtBu)2(NRARB)2] (I), in solution in each case, is not to be further reacted directly but instead isolated and then stored and/or used further, its isolation may comprise one or more steps.
In a variant of the method, the isolation of [W(NtBu)2(NRARB)2] (I) comprises applying a negative pressure px to an interior of the respective reaction vessel. The negative pressure px, as a function of the other reaction conditions, in particular as a function of the solvent, is for example, 10−3 to 101 mbar. This makes it possible, for example, to completely or almost completely separate and recycle the solvent or solvent mixture from step b). This is particularly advantageous from an economical and ecological point of view. By applying such a low negative pressure, tBuNH2 released during the reaction and, generally, unreacted amine HNRARB are also removed. In order to remove the latter quantitatively, a greater negative pressure, depending on the amine HNRARB, may optionally be selected.
In this way, that is, by applying such a low negative pressure, when [W(NtBu)2(NMe2)2] was isolated, dimethylamine, which is unreacted or used as solvent, and tertbutylamine released during the reaction in step b) were removed easily and quantitatively. Further purification of the compound remaining in the respective reaction vessel [W(NtBu)2(NMe2)2], by transcondensation or distillation for example, was not required, according to NMR spectroscopic analysis. This is because extraneous signals by impurities, by-products or decomposition products were not observed in the 1H-NMR or in the 13C-NMR spectrum of [W(NtBu)2(NMe2)2].
The isolation of [W(NtBu)2(NRARB)2] (I) may also comprise one or more of the following method steps: the reduction in the volume of the mother liquor, i.e. concentration, for example by means of “bulb-to-bulb”, the addition of a solvent and/or a solvent exchange, in order to achieve precipitation of the product from the mother liquor and/or to remove impurities and/or educts, washing and drying of the product. Furthermore, it can be provided that the isolation comprises distillation and/or sublimation and/or recrystallization.
Generally, no purification is necessary for a later reaction or use of the product [W(NtBu)2(NRARB)2] (I) after its isolation. However, it is possible, for example, to provide transcondensation and/or distillation and/or sublimative purification.
With the claimed method for the production of bis(tertbutylimido)bis(dialkylamido)tungsten compounds according to the general formula [W(NtBu)2(NRARB)2] (I), the disadvantages of the prior art are overcome. In particular, the compounds obtainable by the claimed method are inherently free of lithium impurities, due namely to the absence of lithium-containing educts, such as, for example, lithium dimethylamide. They are, therefore, particularly suitable as precursors for the deposition of tungsten layers or tungsten-containing layers.
The object is further achieved by bis(tertbutylimido)bis(dialkylamido)tungsten compounds according to the general formula
[W(NtBu)2(NRARB)2] (I),
wherein
RA and RB are independently selected from the group consisting of linear and branched alkyl radicals having 1 to 20 carbon atoms, obtainable by a method for the production of bis(tertbutylimido)bis(dialkylamido)tungsten compounds according to one of the exemplary embodiments described above.
The bis(tertbutylimido)bis(dialkylamido)tungsten compounds according to the general formula [W(NtBu)2(NRARB)2] (I) can advantageously be produced particularly easily and economically in a two-stage synthesis. The compounds of the type [W(NtBu)2(NRARB)2] (I) are reproducible even without further distillative and/or sublimative purification producible in high purity. However, it is possible, for example, to provide transcondensation and/or distillation and/or sublimative purification. Bis(tertbutylimido)bis(dialkylamido)tungsten compounds according to the general formula [W(NtBu)2(NRARB)2] (I) meet the purity requirements of precursors for the production of high-quality substrates which have tungsten layers or tungsten-containing layers. In particular, they can be produced without the use of lithium-containing educts, such as lithium dimethylamide, and are thus obtainable free from lithium impurities. In addition, the bis(tertbutylimido)bis(dialkylamido) tungsten compounds can also be produced on an industrial scale, wherein comparable yields and purity of the target compounds are achieved. The reproducible yield is satisfactory for [W(NtBu)2(NMe2)2], for example—even when upscaling to an industrial scale.
Bis(tertbutylimido)bis(dialkylamido)tungsten compounds according to the general formula I, such as, for example, [W(NtBu)2(NMe2)2] and [W(NtBu)2(NMe)2], are known. Compounds of the type [W(NtBu)2(NRARB)2], obtainable by a method for the production of bis(tertbutylimido)bis(dialkylamido)tungsten compounds according to one of the exemplary embodiments described above, differ significantly in their properties from those that can be produced by a method of the prior art. The isolated target compounds thus have, without complex purification, at least as high a purity as compounds of the type [W(NtBu)2(NRARB)2], which were produced according to the method of the prior art and purified by means of two fractionating distillations. In particular, they are inherently free from lithium impurities, namely due to the omission of lithium-containing educts, such as, for example, lithium dimethylamide, during their production. If the educt [W(NtBu)2(NHtBu)2] is first produced by reacting Was with tBuNH2 in the presence of an auxiliary base, in steps a) and b) overall—apart from the respectively desired target compound—only defined, comparatively easily separable by-products are produced, typically an ammonium salt, for example tBuNH3Cl, and tBuNH2. Furthermore, excess, i.e. unreacted, amine HNRARB may need to be removed. The relatively easy separability of the ammonium salt precipitating in step a) can also be explained by the advantageous selection of an aprotic solvent. If, for example n-hexane, i-hexane and/or n-heptane are used as solvent, the ammonium salt, for example tBuNH3Cl, is precipitated quantitatively, while the target compound, for example [W(NtBu)2(NMe2)2] remains in solution. Contamination of the respective bis(tertbutylimido)bis(dialkylamido)tungsten complex by the resulting ammonium salt load, for example tBuNH3Cl, is thus advantageously avoided. The tBuNH2 obtained in step b) of the claimed method is comparatively highly volatile and can thus also be easily quantitatively removed, namely by applying a slight negative pressure to an interior of the respective reaction vessel. The same generally applies to the HNRARB used in excess in step b), in particular to very highly volatile amines, such as, for example, HNMe2. Furthermore, it is advantageous that undefinable byproducts are not formed, for example lithium tungstate complex salts, which can only be separated with difficulty or not at all. It is particularly advantageous that the ammonium salt, for example tBuNH3Cl, produced in step a) can be removed easily and quantitatively by a filtration step before the reaction in step b). The compound of the type [W(NtBu)2(NRARB)2] (I), which is in solution in each case after step b) is carried out, may be isolated, for example, simply by removing all volatile constituents. Furthermore, the isolated compound has neither amine impurities nor residues of the solvent or solvent mixture used. The respective target compound can thus be used and/or stored after isolation without further purification.
In one embodiment of the bis(tertbutylimido)bis(dialkylamido)tungsten compounds according to the general formula [W(NtBu)2(NRARB)2] (I), obtainable by a method for the production of bis(tertbutylimido)bis(dialkylamido)tungsten compounds according to one of the exemplary embodiments described above, RA and RB are independently selected from the group consisting of Me, Et, nPr, iPr, nBu, tBu, sBu, iBu, CH2sBu, CH2iBu, CH(Me)(iPr), CH(Me)(nPr), CH(Et)2, C(Me)2(Et), C6H11, CH2C6H5 and C6H5. Exemplary compounds are [W(NtBu)2(NMe2)2] and [W(NtBu)2(NEtMe)2].
In another embodiment of the bis(tertbutylimido)bis(dialkylamido)tungsten compounds according to the general formula [W(NtBu)2(NRARB)2] (I), obtainable by a method for the production of bis(tertbutylimido)bis(dialkylamido)tungsten compounds according to one of the exemplary embodiments described above, R is selected from the group consisting of 2-fluoroethyl, 2,2-dichloro-2-fluoroethyl, 2-chloroethyl, 2-bromoethyl, 2,2-dibromoethyl, 2,2,2-tribromoethyl, hexafluoroisoprophyl, (2,2-dichlorocyclopropyl)methyl and (2,2-dichloro-1-phenyl-cyclopropyl)methyl.
Owing to their purity, in particular the absence of lithium impurities, the compounds according to the general formula [W(NtBu)2(NRARB)2] (I) that can be produced with the claimed method are particularly well suited as precursors for the production of a high-quality tungsten layer or tungsten-containing layer on a surface of a substrate.
The object is also achieved by the use of a bis(tertbutylimido)bis(dialkylamido)tungsten compound according to the general formula
[W(NtBu)2(NRARB)2] (I),
wherein
RA and RB are independently selected from the group consisting of linear and branched alkyl radicals having 1 to 20 carbon atoms,
This is a method for the production of a tungsten layer or a tungsten-containing layer on a surface of a substrate
using a bis(tertbutylimido)bis(dialkylamido)tungsten compound according to the general formula [W(NtBu)2(NRARB)2] (I),
The tungsten-containing layer may be, for example, a layer of WN, WON, WSi, WSiN or WO.
The term “layer” is synonymous with the expression “film” and does not make any statement regarding the layer thickness or the film thickness. Corundum foils or thin metallic foils can, for example, be used as the substrate. The substrate itself can be part of a component. The tungsten layer or the tungsten-containing layer can be deposited by means of a vapor deposition method, in particular by means of various ALD methods (atomic layer deposition) and CVD methods (chemical vapor deposition).
Due to their high purity, the bis(tertbutylimido)bis(dialkylamido)tungsten compounds used are particularly well suited as precursors for the production of high-quality tungsten layers and tungsten-containing layers on a surface of a substrate. In particular, due to the method used for their production, unlike the compounds obtainable by means of the known method, they are inherently free from lithium impurities which are disadvantageous for the coating process and thus for the performance of the coated substrates.
In one embodiment of the use of a bis(tertbutylimido)bis(dialkylamido)tungsten compound according to the general formula [W(NtBu)2(NRARB)2] (I), obtained or obtainable by a method for the production of bis(tertbutylimido)bis(dialkylamido)tungsten compounds according to one of the previously described exemplary embodiments, for the production of a tungsten layer or a tungsten-containing layer on a surface of a substrate or in one embodiment of the method for the production of a tungsten layer or a tungsten-containing layer on a surface of a substrate, the substrate is a wafer. The wafer may comprise silicon, silicon carbide, germanium, gallium arsenide, indium phosphide, a glass, such as SiO2, and/or a plastic, such as silicone, or consist entirely of one or more such materials. The wafer can also have one or more wafer layers, each having one surface. The production of the tungsten layer or the tungsten-containing layer may be provided on the surface of one or more wafer layers.
The object is further achieved by bis(tertbutylimido)bis(dialkylamido)tungsten compounds according to the general formula
[W(NtBu)2(NRARB)2] (I),
wherein
RA and RB are independently selected from the group consisting of linear and branched alkyl radicals having 1 to 20 carbon atoms,
wherein
the bis(tertbutylimido)bis(dialkylamido)tungsten compounds [W(NtBu)2(NMe2)2] and [W(NtBu)2(NEtMe)2], are excluded.
The bis(tertbutylimido)bis(dialkylamido)tungsten compounds according to the general formula [W(NtBu)2(NRARB)2] (I) can advantageously be produced particularly easily and economically in a two-stage synthesis. The compounds of the type [W(NtBu)2(NRARB)2] (I) can be produced reproducibly in high purity, even without any further distillative and/or sublimative purification. However, it is possible, for example, to provide transcondensation and/or distillation and/or sublimative purification. The bis(tertbutylimido)bis(dialkylamido)tungsten compounds according to the general formula [W(NtBu)2(NRARB)2] (I) meet the purity requirements of precursors for the production of high-quality substrates which have tungsten layers or tungsten-containing layers. In particular, they can be produced without the use of lithium-containing educts, such as lithium dimethylamide, and are thus obtainable free from lithium impurities. In addition, the bis(tertbutylimido)bis(dialkylamido) tungsten compounds can also be is produced on an industrial scale, wherein comparable yields and purity of the target compounds are achieved.
Owing to their purity, in particular the absence of lithium impurities, and the fact that they can be produced easily and economically on an industrial scale, compounds according to the general formula [W(NtBu)2(NRARB)2] (I) are particularly well suited as precursors for the production of a high-quality tungsten layer or tungsten-containing layer on a surface of a substrate.
The object is also achieved by the use of bis(tertbutylimido)bis(dialkylamido)tungsten compounds according to the general formula
[W(NtBu)2(NRARB)2] (I),
wherein
RA and RB are independently selected from the group consisting of linear and branched alkyl radicals having 1 to 20 carbon atoms,
for the production of a tungsten layer or a tungsten-containing layer on a surface of a substrate,
wherein the bis(tertbutylimido)bis(dialkylamido)tungsten compound [W(NtBu)2(NMe2)2] is excluded,
The invention relates to a method for the production of a tungsten layer or a tungsten-containing layer on a surface of a substrate
using a bis(tertbutylimido)bis(dialkylamido)tungsten compound according to the general formula [W(NtBu)2(NRARB)2] (I), wherein
RA and RB are independently selected from the group consisting of linear and branched alkyl radicals having 1 to 20 carbon atoms,
comprising the steps of:
a) providing the bis(tertbutylimido)bis(dialkylamido)tungsten compound according to the general formula [W(NtBu)2(NRARB)2] (I)
and
b) depositing the tungsten layer or the tungsten-containing layer on the surface of the substrate.
The tungsten-containing layer may be, for example, a layer of WN, WON, WSi, WSiN or WO.
The term “layer” is synonymous with the expression “film” and does not make any statement regarding the layer thickness or the film thickness, Corundum foils or thin metallic foils can, for example, be used as the substrate.
The substrate itself can be part of a component. The tungsten layer or the tungsten-containing layer can be deposited by means of a vapor deposition method, in particular by means of various ALD methods (atomic layer deposition) and CVD methods (chemical vapor deposition).
Due to their high purity, the bis(tertbutylimido)bis(dialkylamido)tungsten compounds used are particularly well suited as precursors for the production of high-quality tungsten layers and tungsten-containing layers on a surface of a substrate. In particular, due to the method used for their production, unlike the compounds obtainable by means of the known method, they are inherently free from lithium impurities which are disadvantageous for the coating process and thus for the performance of the coated substrates.
In one embodiment of the use of a bis(tertbutylimido)bis(dialkylamido)tungsten compound according to the general formula [W(NtBu)2(NRARB)2] (I) for the production of a tungsten layer or a tungsten-containing layer on a surface of a substrate or in one embodiment of the method for the production of a tungsten layer or a tungsten-containing layer on a surface of a substrate, the substrate is a wafer. The wafer may comprise silicon, silicon carbide, germanium, gallium arsenide, indium phosphide, a glass, such as SiO2, and/or a plastic, such as silicone, or consist entirely of one or more of said materials. The wafer can also have one or more wafer layers, each having one surface. The production of the tungsten layer or the tungsten-containing layer may be provided on the surface of one or more wafer layers.
The object is further achieved by a substrate which has a tungsten layer or a tungsten-containing layer on a surface,
wherein the tungsten layer of the tungsten-containing layer can be produced using a bis(tertbutylimido)bis(dialkylamido)tungsten compound according to the general formula [W(NtBu)2(NRARB)2] (I),
obtained or obtainable according to a method for the production of bis(tertbutylimido)bis(dialkylamido)tungsten compounds according to one of the exemplary embodiments described above,
wherein RA and RB are independently selected from the group consisting of linear and branched alkyl radicals having 1 to 20 carbon atoms.
Moreover, the object is further achieved by a substrate which has a tungsten layer or a tungsten-containing layer on a surface,
wherein the tungsten layer of the tungsten-containing layer can be produced using a bis(tertbutylimido)bis(dialkylamido)tungsten compound according to the general formula [W(NtBu)2(NRARB)2] (I),
wherein RA and RB are independently selected from the group consisting of linear and branched alkyl radicals having 1 to 20 carbon atoms,
wherein the bis(tertbutylimido)bis(dialkylamido)tungsten compound [W(NtBu)2(NMe2)2] is excluded.
The tungsten-containing layer may be, for example, a layer of WN, WCN, WSi, WSiN or WO.
The term “layer” is synonymous with the expression “film” and does not make any statement regarding the layer thickness or the film thickness. Corundum foils or thin metallic foils can, for example, be used as the substrate. The substrate itself can be part of a component. The tungsten layer or the tungsten-containing layer can be deposited by means of a vapor deposition method, in particular by means of various ALD methods (atomic layer deposition) and CVD methods (chemical vapor deposition).
Owing to their high purity, the bis(tertbutylimido)bis(dialkylamido)tungsten compounds used are particularly well suited as precursors for the production of high-quality tungsten layers and tungsten-containing layers. In particular, due to the method used for their production, unlike the compounds obtainable by means of the known method, they are inherently free from lithium impurities which are disadvantageous for the coating process and thus for the performance of the coated substrates.
In one embodiment of the substrate, which has on a surface a tungsten layer or a tungsten-containing layer, wherein the tungsten layer or the tungsten-containing layer can be produced using a bis(tertbutylimido)bis(dialkylamido)tungsten compound according to the general formula [W(NtBu)2(NRARB)2] (I), obtained or obtainable, in particular, by a method for the production of bis(tertbutylimido)bis(dialkylamido)tungsten compounds according to one or more of the exemplary embodiments described above, the substrate is a wafer. The wafer may comprise silicon, silicon carbide, germanium, gallium arsenide, indium phosphide, a glass, such as SiO2, and/or a plastic, such as silicone, or consist entirely of one or more of said materials. The wafer can also have one or more wafer layers, each having one surface. The production of the tungsten layer or the tungsten-containing layer may be provided on the surface of one or more wafer layers.
The object is further achieved by the use of a bis(tertbutylimido)bis(dialkylamido)tungsten compound according to the general formula [W(NtBu)2(NRARB)2] (I), obtained or obtainable by a method for the production of bis(tertbutylimido)bis(dialkylamido)tungsten compounds according to one of the previously described exemplary embodiments, for the production of an electronic component. In the context of the present invention, the term “electronic component” is also intended to mean “electronic part”.
This is a method for the production of an electronic component using a bis(tertbutylimido)bis(dialkylamido)tungsten compound according to the general formula [W(NtBu)2(NRARB)2] (I),
obtained or obtainable according to a method for the production of bis(tertbutylimido)bis(dialkylamido)tungsten compounds according to one of the exemplary embodiments described above,
wherein
RA and RB are independently selected from the group consisting of linear and branched alkyl radicals having 1 to 20 carbon atoms,
comprising the steps of:
a) providing the bis(tertbutylimido)bis(dialkylamido)tungsten compound according to the general formula [W(NtBu)2(NRARB)2] (I),
b) depositing a tungsten layer or a tungsten-containing layer on a surface of a substrate,
and
c) completing the electronic component.
The object is further achieved by a method for the production of an electronic component using a bis(tertbutylimido)bis(dialkylamido)tungsten compound according to the general formula [W(NtBu)2(NRARB)2] (I), using a bis(tertbutylimido)bis(dialkylamido)tungsten compound according to the general formula [W(NtBu)2(NRARB)2] (I),
wherein
RA and RB are independently selected from the group consisting of linear and branched alkyl radicals having 1 to 20 carbon atoms,
wherein the bis(tertbutylimido)bis(dialkylamido)tungsten compound [W(NtBu)2(NMe2)2] is excluded,
comprising the steps of:
a) providing the bis(tertbutylimido)bis(dialkylamido)tungsten compound according to the general formula [W(NtBu)2(NRARB)2] (I) ,
b) depositing a tungsten layer or a tungsten-containing layer on a surface of a substrate,
and
c) completing the electronic component.
In the context of the present invention, the term “electronic component” is also intended to mean “electronic part”.
Owing to their purity, the bis(tertbutylimido)bis(dialkylamido)tungsten compounds used are particularly well suited as precursors for the production of high-quality substrates which have tungsten layers or tungsten-containing layers. Said substrates are used for the production of electronic components and electronic parts. In addition, bis(tertbutylimido)bis(dialkylamido)tungsten compounds used can be produced particularly easily and economically in good and reproducible yields and high purity by means of a two-stage synthesis described above. In particular, they can be produced lithium-free by means of the method claimed here. They are, therefore, suitable for use on an industrial scale.
With the claimed method, defined bis(tertbutylimido)bis(dialkylamido)tungsten compounds can be produced easily, economically and reproducibly in high purity and good yields. The compounds, which can be produced in a two-stage synthesis, already have a high purity after their isolation according to 1H-NMR spectra. No complex purification of the respectively isolated raw product by fractionating distillation and/or sublimation is required for this purpose. However, transcondensation and/or distillation and/or sublimation and/or crystallization and/or recrystallization may be provided. Owing to their high purity, in particular the absence of lithium impurities and impurities due to inorganic salts, the compounds producible by the claimed method are suitable for use as precursors for the production of high-quality substrates which have tungsten layers or tungsten-containing layers. The compounds of the general formula [W(NtBu)2(NRARB)2] (I) may, because of their high purity, be used, for example, to produce high-quality contact materials, barrier layers, electrodes for thin film capacitors and field effect transistors, each consisting of or comprising, for example, tungsten nitride layers. In addition, the method claimed is characterized in that it can also be carried out on an industrial scale, with a comparable yield and purity of the target compounds. Overall, the claimed method is to be assessed as satisfactory from an ecological and economic point of view,
Other features, details, and advantages of the invention follow from the wording of the claims as well as from the following description of exemplary embodiments.
Process Specifications for the Synthesis of [W(NtBu)2(NHtBu)2] and [W(NtBu)2(NMe2)2]
All reactions were carried out in a protective gas atmosphere. Work was carried out using conventional Schlenk techniques, with nitrogen or argon being used as protective gas. The corresponding vacuum rakes or Schlenk lines were connected to rotary vane pumps made by Vacuubrand. The educts, reagents and synthesized products were weighed and stored in glove boxes made by MBraun (model MB 150 8G-1 or Lab Master 130) under a nitrogen atmosphere.
The deuterated solvent C6D6 was dehydrated over a K/Na alloy, then condensed and stored over a molecular sieve.
All nuclear magnetic resonance spectroscopic measurements were performed in automated mode on an AV II 300 instrument or in manual mode on an AV III HD 250 or AV III HD 300 instrument. 1H and 13C-NMR spectra were calibrated to the corresponding residual proton signal of the solvent as an internal standard: 1H-NMR spectra: C6D6: 7.16 ppm (s); 13C-NMR spectra: C6D6: 128.0 ppm (tr). The chemical shifts are indicated in ppm and refer to the δ scale. All signals are provided with the following abbreviations according to their splitting pattern: s (singlet).
In substance, the measurements of infrared spectra were usually performed on an Alpha ATR-IR spectrometer made by Bruker. The absorption bands are indicated in wave number (cm−1), and the intensity is described with the following abbreviations: w (weak), m (medium strong), st (strong), vst (very strong). The spectra were always normalized to the band with the highest intensity.
The elemental analyses were carried out on a vario MICRO cube combustion device made by Elementar. Sample preparation was carried out in a glove box flooded with nitrogen by weighing the substance in tin crucibles, which were cold-welded and stored in a protective gas atmosphere until measurement. The elements of hydrogen, carbon and nitrogen were determined by means of a combustion analysis, wherein the information is always given in mass percent.
All EI mass spectrometric investigations were performed on an AccuTOF GCv spectrometer made by Joel. Air-sensitive and moisture-sensitive samples were prepared in a glove box in crucibles and stored in a protective gas atmosphere until measurement. In the case of high-resolution spectra, the signal with the highest intensity of the isotope pattern is respectively indicated.
The thermogravimetric investigations were performed on a TGA/DSC 3+ STAR system made by Mettler Toledo. In the process, a coupled SDTA measurement was performed for each TGA. The sample was measured in an aluminum oxide, aluminum or sapphire crucible, depending on the method or state of aggregation. The sample was heated at a specific heating rate from 25° C. to the final temperature. The evaluation of the spectra obtained was carried out with STARe software made by Mettler Toledo.
The synthesis was carried out based on a specification of Nugent and Harlow. (W. A. Nugent, R. L. Harlow, Inorg. Chem. 1980, 19, 777-779)
tBuNH2 (21.0 g, 287 mmol, 11.4 equiv.) was added to 350 mL n-hexane and WCl6 (10.0 g, 25.2 mmol, 1.00 equiv.) was added in portions at room temperature. The reaction mixture turned slightly yellow while a colorless solid precipitated out. The reaction mixture was stirred for 72 h at room temperature.
The precipitated solid was filtered off and the solvent of the filtrate was removed in a fine vacuum (10−3 to 10−2 mbar). The product was purified sublimatively at 65° C. in a fine vacuum (10−3 to 10−2 mbar) and obtained as a pale yellow solid with a yield of 71% (8.28 g, 17.6 mmol).
Alternatively, the product can be crystallized from toluene at −24° C. However, the yield is then only 45-51%.
1H-NMR (C6D6, 300 MHz, 300 K): δ/ppm=1.27 (s, 18 H, NCMe3), 1.45 (s, 18 H, NHCMe3), 5.22 (s, 2 H, NHCMe3); 13C-NMR (C6D6, 75 MHz, 300 K): δ/ppm=33.7 (NCMe3), 33.8 (NHCMe3), 53.3 (NHCMe3), 66.0 (NCMe3); TGA (TS=25° C., TE=900° C., 10° C./min): Stages; 1, 3% degradation: 125.3° C., TMA: 195.7° C., total mass degradation: 95.0%; SDTA: TM(Onset): 85.3° C., TM(max): 90.0° C., TD(Onset): 137.3° C., TD(max.): 150.8° C.
[W(NtBu)2(NHtBu)2] (250 mg, 0.53 mmol, 1,00 equiv.) was added, frozen in liquid nitrogen and HNMe2 (5.13 g, 114 mmol, 215 equiv), which had been dried beforehand according to standard methods, condensed. The reaction mixture was slowly heated to −20° C. until [W(NtBu)2(NHtBu)2] dissolved. The pale yellow solution was heated to −15° C. and stirred for 2 h. The orange reaction mixture was brought to room temperature, wherein excess HNMe2 evaporated. Residues of HNMe2 and tBuNH2 produced were removed in a fine vacuum (10−3 to 101 mbar). The product was obtained in the form of an orange liquid with a yield of 93% (206 mg, 0.50 mmol).
1H-NMR (C6D6, 300 MHz, 300 K): δ/ppm=1.41 (s, 18 H, CMe3), 3.51 (s, 12 H, NMe2); 13C-NMR (C6D6, 75 MHz, 300 K); δ/ppm=34.1 (CMe3), 53.8 (NMe2), 66.2 (CMe3); IR: {tilde over (ν)}/cm−1=2965 (m), 2919 (m), 2896 (m), 2857 (m), 2821 (m), 2776 (m), 1450 (m), 1421 (w), 1354 (m), 1288 (m), 1240 (vst), 1212 (st), 1159 (w), 1142 (w), 1125 ('N), 1054 (w), 1024 (w), 975 (st), 958 (vst), 806 (w), 780 (w), 696 (w), 636 (w), 561 (st), 476 (w); Elementary analysis for Cl2H30N4W: calculated; C: 34.79%, H: 7.30%, N: 13.53%, found: C: 33.21%, H: 6.74%, N: 14.89%; HR-EI-MS: calculated for C12H30N4W: 414.1979 m/z, found: 414.1964 m/z; TGA (TS=25° C., TE=600° C., 10° C./min): Stages: 1, 3% degradation: 120.7° C., TMA: 185.2° C., total mass degradation: 97.3%; SDTA: TD(Onset): 150.3° C., TD(max.): 186.9° C.
The invention is not limited to one of the embodiments described above but may be modified in many ways.
It can be seen that the invention relates to a two-stage synthesis for the production of bis(tertbutylimido)bis(dialkylamido)tungsten compounds according to the general formula [W(NtBu)2(NRARB)2] (I), starting from [W(NtBu)2(NHtBu)2]. The invention further relates to compounds according to the general formula [W(NtBu)2(NRARB)2] (I), obtainable according to the claimed method, compounds according to the general formula [W(NtBu)2(NRARB)2] (I), with the exception of [W(NtBu)2(NMe2)2] and [W(NtBu)2(NMe2)2], the use of a compound [W(NtBu)2(NRARB)2] (I) and a substrate which, on a surface, has a tungsten layer or a tungsten-containing layer.
With the described method, defined bis(tertbutylimido)bis(dialkylamido)tungsten compounds of the type [W(NtBu)2(NRARB)2] (I) can be produced easily, efficiently, economically and reproducibly in high purity and good yields. The method can also be carried out on an industrial scale. Already after their isolation, without complex purification, the compounds do not have any NMR spectroscopically detectable impurities. Owing to their high purity, in particular the absence of lithium impurities, they are suitable as precursors for the production of high-quality substrates which have tungsten layers or layers containing tungsten. For example, they are suitable for the production of high-quality contact materials or barrier layers, including, for example, tungsten nitride.
All features and advantages resulting from the claims, the description and the figures, including constructive details, spatial arrangements and method steps, can be essential to the invention, both in themselves and in the most diverse combinations.
| Number | Date | Country | Kind |
|---|---|---|---|
| 18212064.2 | Dec 2018 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2019/082892 | 11/28/2019 | WO | 00 |
